Many non-volatile memory devices are fabricated with semiconductor materials. One such non-volatile memory device is a flash memory array. Flash memory arrays are semiconductor devices that are formed from an array of memory cells with each cell having a floating gate transistor that includes a source, a drain, a floating gate, and a control gate. The sources of each floating gate in each cell are connected to form a source line.
The floating gate transistors of a flash memory array are electrically isolated from one another by isolation structures. One type of isolation structure used is a Shallow Trench Isolation (“STI”) structure. STI structures are generally formed by etching a trench between the cells and filling the trench with a suitable dielectric material. STI structures used in flash memory arrays result in high resistance of the source line, which reduces the operational performance of the memory. In addition, in flash memory arrays there is only one source contact for each source line, which is coupled to the sources of each memory cell in a line of memory cells. Therefore, each memory cell has a different source resistance depending on the location of the memory cell with respect to the source contact. This results in a wide threshold voltage distribution for the entire flash memory array.